Out-of-band communication channel for point-to-multi-point communications

Abstract

Techniques are described for implementing an out-of-band communication channel used to exchange control channel information in sub-carrier-based optical communication systems. In an example implementation, a transmitter includes a laser operable to supply an optical signal, a digital signal processor operable to supply first electrical signals based on first data input to the digital signal processor and second data input to the digital signal processor, digital-to-analog conversion circuitry operable to output second electrical signals based on the first electrical signals, modulator driver circuitry is operable to output third electrical signals based on the second electrical signals, and an optical modulator operable to supply first and second modulated optical signals based on the third electrical signals. The first modulated optical signal includes a plurality of optical subcarriers carrying user data. The plurality of optical subcarriers also being amplitude modulated to carry control information.

What is claimed is: 
     
       1. An apparatus, comprising:
 a laser operable to supply an optical signal; a digital signal processor operable to supply digital signals; 
 digital to analog circuitry operable to provide analog signals based on the digital signals; 
 driver circuitry coupled to the digital to analog circuitry, the driver circuitry operable to supply at least one drive signal; and 
 a modulator operable to:
 receive said at least one drive signal, 
 modulate the optical signal supplied from the laser based on said at least one drive signal to provide a plurality of optical subcarriers, each of the plurality of optical subcarriers having a corresponding one of a plurality of frequencies, 
 amplitude modulate the plurality of optical subcarriers at a first frequency to carry control information, the control information including packets that include information identifying a recipient node of user data, and 
 modulate each of the plurality of subcarriers at a second frequency to carry respective user data at a second frequency greater than the first frequency. 
 
 
     
     
       2. An apparatus in accordance with  claim 1 , wherein each of the optical subcarriers is a Nyquist subcarrier. 
     
     
       3. An apparatus in accordance with  claim 1 , wherein the control information includes OAM&P information. 
     
     
       4. An apparatus in accordance with  claim 1 , wherein the plurality of optical subcarriers is a first plurality of optical subcarriers, the apparatus further including a receiver operable to receive a second plurality of optical subcarriers, each of which is amplitude modulated at a third frequency different than the first frequency and the second frequency. 
     
     
       5. An apparatus in accordance with  claim 4 , wherein the first frequency is within a first band and the third frequency is within a second band. 
     
     
       6. An apparatus in accordance with  1 , wherein the packet includes a preamble, a header, and a payload. 
     
     
       7. An apparatus in accordance with  claim 6 , wherein the packet further includes a postamble. 
     
     
       8. An apparatus in accordance with  claim 1 , wherein the modulator includes a Mach-Zehnder modulator. 
     
     
       9. An apparatus in accordance with  claim 1 , wherein each of the plurality of optical subcarriers includes a first polarization component and a second polarization component. 
     
     
       10. An apparatus in accordance with  claim 1 , wherein the modulator is further operable to collectively amplitude modulate the plurality of optical subcarriers at the first frequency to carry the control information. 
     
     
       11. An apparatus in accordance with  claim 1 , wherein the control information is first control information, the plurality of optical subcarriers is a plurality of first optical subcarriers, and the plurality of frequencies is a plurality of first frequencies, the modulator further being operable to supply a second optical subcarrier having a second frequency that is greater than each of the plurality of first frequencies, the second optical subcarrier carrying second control information. 
     
     
       12. An apparatus in accordance with  claim 1 , wherein the control information is first control information, the plurality of optical subcarriers is a plurality of first optical subcarriers, and the plurality of frequencies is a plurality of first frequencies, the modulator further being operable to supply a second optical subcarrier having a second frequency that is less than each of the plurality of first frequencies, the second optical subcarrier carrying second control information. 
     
     
       13. An apparatus in accordance with  claim 1 , wherein the control information is first control information, the plurality of optical subcarriers is a plurality of first optical subcarriers, and the plurality of frequencies is a plurality of first frequencies, the modulator further being operable to supply: a second optical subcarrier having a second frequency that is greater than each of the plurality of first frequencies, the second optical subcarrier carrying second control information; and a third optical subcarrier having a third frequency that is less than each of the plurality of first frequencies, the third optical subcarrier carrying third control information. 
     
     
       14. An apparatus in accordance with  claim 1 , wherein the digital signal processor includes a plurality of gain circuits, each of which having an associated one of a plurality of gains, each of the digital signals being indicative of a corresponding one of the plurality of gains. 
     
     
       15. An apparatus in accordance with  claim 1 , wherein the apparatus includes a transceiver, wherein the plurality of subcarriers is a first plurality of subcarriers, the transceiver including a receiver operable to receive a second plurality of subcarriers. 
     
     
       16. An apparatus in accordance with  claim 1 , wherein the first frequency is in a range of 3 MHz to 4 MHz.